This invention relates to the delivery of dental adhesives and particularly to the delivery of dental adhesives in small or single dose quantities. The invention is more particularly applicable to the delivery of dental adhesives for the bonding of orthodontic appliances to teeth.
Providing dental adhesives to dental practitioners in a form that they can be efficiently used and so that excess quantities are not exposed or wasted has been the subject of a number of efforts. Single dose delivery systems have been developed in which a dental adhesive or composite of a quantity that is no greater than that needed for a single application or as a single dose include, for example, the delivery system described in U.S. Pat. No. 5,860,806, hereby expressly incorporated herein by reference.
With the development of orthodontic brackets such as those described, for example in U.S. Pat. No. 4,068,379, the orthodontic brackets with bases for adhesive bonding to teeth have replaced tooth encircling bands as the primary appliances for connecting orthodontic archwires to teeth. With banded appliances, archwire supports mounted on bands encircle the teeth to hold the archwire supports in place on the teeth. Brackets, on the other hand, rely solely on an adhesive bond between the base or pad of the bracket and the surface of the crown of the tooth. Adequate bond strength between the teeth and the bracket bases has traditionally required the dentist or an assistant to dispense adhesive onto the bracket at chairside, using single or multiple part dental adhesives specifically developed for securing orthodontic appliances to teeth. Popular single part adhesives are cured by ultraviolet light, while multiple part adhesives cure chemically, following the mixing of the adhesive immediately preceding use. Multiple part or chemical cure adhesives are often capable of producing bonds that are stronger than with the light cured adhesives.
The application of adhesives to brackets at chairside is a time consuming activity for a dental or orthodontic practitioner. In preparing adhesive at chairside, the quantity of adhesive dispensed must be carefully controlled by the orthodontist or other office personnel. Cleanup is required, which must be done by the doctor, whose time is expensive. The handling of brackets during the application of adhesive can result in misorientation of the appliances or a mixup of appliances, which are usually each designed to fit a specific tooth.
One attempt to minimize the chairside handling of adhesives in the application of orthodontic appliances to teeth has been the introduction of orthodontic brackets with light cured adhesive pre-applied to the bracket bases. While these brackets with pre-applied adhesive are attractive to orthodontists for their promise of convenience and ease of installation on the teeth of the patient, such brackets have been associated with an increased failure rate of the bond between the bracket bases and the teeth.
One cause of failures of the bonds between the bracket and a tooth is due to the use of an adhesive beyond its actual shelf life. The shelf life of adhesive that has been pre-applied to brackets is optimistically claimed to be twenty-four months. In practice, environmental factors, such as heat, humidity, etc., during transit and storage of the brackets having the pre-applied adhesives, shorten the shelf life of the adhesive. Furthermore, orthodontic brackets with adhesives pre-applied seldom reach the offices of orthodontists immediately following manufacture, so that some portion of the shelf life of the adhesive is already spent by the time the brackets are received into inventory by the orthodontist. In addition, careful records and careful inventory control by the doctor is required to insure that all adhesively pre-coated brackets are used in a first-in first-out (FIFO) basis and before the adhesive becomes too old.
Orthodontic brackets are often stocked by orthodontists in sufficient quantities so that the doctor has available appliances of various types and sizes to use on any common occasion in the treatment of patients. Maintaining appliance inventories necessarily requires that certain appliances will be in inventory longer than others. Ordinarily, orthodontic brackets are made of metal or other materials that have shelf lives that exceed the technological lives of the appliance, that is, the appliance can usually be stored until it is used or becomes obsolete, which can be many years from the stocking of the appliance by the doctor. Orthodontic brackets have a cost of several dollars each to the doctor, for example, four U.S. dollars per bracket at the time of this patent application. The cost of the adhesive used to secure orthodontic brackets to teeth is substantially less than the cost of an ordinary bracket. A single dose of adhesive, that is, the amount of adhesive necessary to secure a single orthodontic bracket to a tooth, varies from a few cents when supplied separately to about a 75 cent/bracket price premium charged by an adhesively pre-coated bracket manufacturer. As a result, the pre-application by a bracket manufacturer of a few cents worth of adhesive to the base of a bracket has the undesirable effect of limiting the shelf life of a relatively expensive orthodontic appliance.
There are additional disadvantages to the adhesively pre-coated orthodontic appliances currently available to orthodontists. The packaging of such appliances, for example, is quite expensive to produce and is bulky. One hundred cases, for example, might occupy several cubic feet of space in a dentist""s office, which is equal, for example, to that occupied by a small appliance or piece of furniture. Individual brackets having pre-applied adhesive are packaged in sealed packages which must be individually opened at chairside. Appliance delivery systems cannot readily accommodate these brackets or bracket packages, and separate systems for dispensing adhesive primer must be used. Only one part, light curable adhesives, can be pre-applied to brackets. Use of multiple part adhesives, which can be up to thirty percent stronger, is not practical for use on pre-coated brackets. Furthermore, when the amount of pre-applied adhesive appears to be incorrect in a particular situation, there is no easy way for the orthodontic practitioner to adjust the quantity of adhesive in the dentist""s office.
Accordingly, there is a great need on the part of orthodontic practitioners for a system for easily and conveniently applying orthodontic appliances to teeth with adhesive that does not have all of the disadvantages of the pre-adhesively coated orthodontic brackets of the prior art.
A primary objective of the present invention is to provide a dental practitioner a convenient supply of dental adhesive that can be used with a maximum reliability and efficiency and minimum amount of waste and mess. A particular objective of the invention is to provide such a supply of adhesive to an orthodontic practitioner for use in bonding orthodontic brackets to teeth.
A further objective of the present invention is to provide an orthodontic practitioner the advantages that adhesively pre-coated brackets have over the chairside application of adhesive from bulk sources to orthodontic appliances and overcoming the disadvantages of the adhesively pre-coated brackets of the prior art.
According to principles of the present invention, single doses of dental adhesive are provided on substrates and enclosed over an area of the card with a removable cover. The doses of adhesive are provided by dispensing one or more metered amounts of adhesive, preferably in the form of a high viscosity liquid or a paste, onto an area of the substrate, preferably in the form of a disposable card, over which a protective cover is secured. The cover keeps the adhesive out of contact with objects during shipping and handling, and sufficiently prevents exposure of the adhesive to chemicals or light or whatever other medium would tend to set or cure the adhesive so as to preserve the normal expected shelf life of the adhesive.
In the preferred embodiments of the invention, individual appliance doses of orthodontic adhesive are provided to an orthodontist separate from the orthodontic appliances that the adhesive is designed to bond to teeth. Individual doses of such orthodontic adhesive are provided in a form for direct transfer to the bases of orthodontic appliances at chairside. Further, individual adhesive doses are packaged for easy use, and are presented in combination with, or in an arrangement by which they can be easily associated with, specific orthodontic appliances for each of the teeth of a patient.
In accordance with certain principles of the present invention, there is provided an adhesive delivery system and method in which a substrate is provided having a deformable, compliant or conformable surface that allows an edge of a rigid object to be swiped over the surface and cleanly remove from the surface a single dose of adhesive that has been deposited thereon. On such surface, one or more single dose amounts of adhesive, such as orthodontic or other dental adhesive, are supported on separate transfer areas from which they can be effectively transferred to a rigid object such as a tool, a restoration, or the base of an orthodontic appliance, by contact of the object with the substrate, preferably by such swiping motion of the object along the substrate to efficiently scrape the measured dose of adhesive from the substrate surface onto the object. The substrate is preferably provided with a resilient core and a surface that is relatively low friction, non-stick, non-absorbent, vapor-proof and flexible.
At least one, and preferably one for each appliance of an appliance set or other object, single-dose quantity of adhesive is pre-dispensed onto the substrate surface. The preferred adhesive is a non-volatile liquid or paste dental adhesive. Each dose is pre-dispensed onto an adhesive transfer area on the adhesive supporting surface of the substrate. The adhesive is contained in a cavity over the substrate by a vapor-proof cover that is sealed to the substrate surface so as to form a raised enclosure covering the adhesive transfer area or areas of the adhesive supporting surface. Preferably, a plurality of separate cavities is formed between the cover and the substrate surface, one for each of the adhesive transfer areas and each containing one single dose amount of the adhesive. However, the cover may be configured so that a set or sub-set of doses is sealed in a cavity or volume. Preferably, the cover is configured so as to remain out-of-contact with the adhesive on the adhesive transfer areas of the substrate surface. The cover may be configured to open the cavities and expose the doses individually or to expose several or all of a set of doses simultaneously.
In accordance with certain preferred embodiments of the invention, orthodontic appliance holders are provided, one for each adhesive transfer area, and each holder is configured to hold an orthodontic appliance in a ready position relative to a dose of adhesive for easy pickup by an orthodontist. One holder is preferably provided for the support of each appliance needed to treat a particular patient at a particular sitting. In certain embodiments of the invention, an orthodontic appliance is also provided, and preferably a set of appliances is provided, with each appliance associated with each adhesive transfer area that contains a single appliance dose of adhesive, providing the orthodontist with a complete orthodontic appliance system of the components needed to treat a case. All of the doses may be provided of the same adhesive quantity or the doses may be varied in accordance with the requirements for the different appliances of the set. The appliances may, in certain embodiments, be provided pre-attached, one to each holder. Preferably, the appliances are provided physically separate from the substrate bearing the adhesive, and may be provided on holders that are separate or detachable from the substrate bearing the adhesive. The appliances, where provided, are also preferably individually wrapped in their own sanitary containers and are positioned and oriented in their packages for easy pickup by the practitioner.
The system of the preferred embodiment of the invention is further provided with a sealant in a quantity suitable for preparing the teeth on which appliances are to be applied by the adhesive on the substrate. Single or multiple part sealers may be used, and each part is provided in a separate container either affixed to or separate from the substrate, along with such brushes or other applicators as may be convenient.
In certain preferred embodiments of the invention, each of the doses of adhesive is deposited onto the surface of the substrate in a strip that is narrower than the, width of an appliance base or tool edge that will come contact the substrate surface to scoop up the adhesive dose. Each strip of adhesive on the substrate is of a volume that is nominally the minimum required to effectively bond an appliance to a tooth. In addition, separate measured supplemental amounts, preferably one or two in number, each equal to about one tenth of the nominal volume, are deposited on each transfer area of the substrate surface in line with, but separated from, the main nominal adhesive dose. This allows the clinician the option of increasing the nominal main dose by ten or twenty percent on an appliance-by-appliance basis.
In certain preferred embodiments of the invention, a single dose adhesive such as typical light curable adhesives may be used and deposited on the transfer areas of the substrate surface in a contiguous strip. In alternative embodiments, multiple part adhesives may be deposited on the transfer areas of the substrate surface in separate fragmentary amounts such as in dot arrays, for example, by printing spots of each component in interleaved arrays on the substrate surface, in a pattern that lies in a line that is of a width less than the width of an appliance in contact with the substrate surface.
In the preferred embodiment of the invention, the substrate is formed in multiple layers, including an inner core of a thickness of a resilient foam material covered by a film of polyethylene or comparable non-stick flexible material. The cover is preferably also formed of multiple layers, preferably including a polymer layer and a foil layer.
In use, the doctor first opens and applies the sealant to the tooth of a patient. Then, the doctor removes the cover from a substrate on which the dose or doses of adhesive needed for treatment are deposited, exposing the adhesive. The appliance is then picked up, preferably from a holder attached to the substrate carrying the adhesive which holds a specific appliance for installation on a specific tooth of a patient. The appliance so picked up, for example, with tweezers or special tool, is scraped along the pattern of adhesive in one of the transfer areas of the substrate surface, causing the adhesive deposited on the transfer area of the surface to be cleanly removed from the substrate surface and transferred onto the base of the appliance. With a single part adhesive, the appliance is placed on the tooth and, if appropriate, the adhesive is light cured. With the multiple part adhesive, the scraping and removal of the adhesive from the substrate surface causes the separate amounts of the different parts of the adhesive to be thoroughly mixed together so that, upon application onto the surface of the tooth, the adhesive is sufficiently mixed to properly chemically cure.
The delivery system and method of the present invention provides the advantage that orthodontic adhesive, even though not pre-dispensed, can be easily picked up directly by the appliance. Further, the adhesive can be picked up by the appliance in a quantity that is either predetermined at, or that can be adjusted about, a nominal adhesive volume. As a result, the clinician is provided with control over the quantity of adhesive required in varying clinical situations, minimizing cleanup due to excess or minimizing the need for rebonding due to failure from inadequate adhesive.
With the delivery system of the present invention, the adhesive is not attached to the appliance or associated with its package; and thus, the shelf life of the adhesive does not impose a shelf life on the substantially more expensive appliance. The adhesive system of the present invention presents a low cost package of single dose adhesives in a form that can be disposed of separate from the appliances when an adhesive expiration date is reached. Further, the adhesive package, according to preferred embodiments the present invention, is inexpensive and occupies very little space in shipping or in the office of the practitioner.
The preferred embodiments of the invention further provide the advantages of single dose adhesive units, one for each appliance required to treat a single patient, and in a package by which all individual dose units can be opened at once, with minimal handling by the doctor or staff. In certain embodiments of the invention, adhesive primer is provided in a disposable, no-mix, non-light cure form. Further, certain embodiments of the invention provide adhesive light cure as well as multiple part chemical cure compositions. In additional embodiments, individual appliances are packaged in association with each of the single adhesive doses, which may vary in size from appliance-to-appliance.
These and other objectives and advantages of the present invention will be more readily apparent from the following detailed description of the drawings of the preferred embodiment of the invention, in which: